Noms au pluriel

Sarrau? Never heard this word!
This is the important to know, the rule that every French little boy or little girl learn at school:
bijoux, cailloux, choux, genoux, hiboux, joujoux, poux
That's the list of the 7 nouns to know that have an irregular ou-plural. They have an "x" instead of the regular "s".
bijou = jewel, caillou = stone, chou = cabbage. genou = knee. hibou = owl. joujou = little toy. pou = louse.